Age-related changes in visual encoding strategy preferences during a spatial memory task.

Ageing is associated with declines in spatial memory, however, the source of these deficits remains unclear. Here we used eye-tracking to investigate age-related differences in spatial encoding strategies and the cognitive processes underlying the age-related deficits in spatial memory tasks. To do so we asked young and older participants to encode the locations of objects in a virtual room shown as a picture on a computer screen. The availability and utility of room-based landmarks were manipulated by removing landmarks, presenting identical landmarks rendering them uninformative, or by presenting unique landmarks that could be used to encode object locations. In the test phase, participants viewed a second picture of the same room taken from the same (0°) or a different perspective (30°) and judged whether the objects occupied the same or different locations in the room. We found that the introduction of a perspective shift and swapping of objects between encoding and testing impaired performance in both age groups. Furthermore, our results revealed that although older adults performed the task as well as younger participants, they relied on different visual encoding strategies to solve the task. Specifically, gaze analysis revealed that older adults showed a greater preference towards a more categorical encoding strategy in which they formed relationships between objects and landmarks.

Age-related differences in visual encoding and response strategies contribute to spatial memory deficits.

Successful navigation requires memorising and recognising the locations of objects across different perspectives. Although these abilities rely on hippocampal functioning, which is susceptible to degeneration in older adults, little is known about the effects of ageing on encoding and response strategies that are used to recognise spatial configurations. To investigate this, we asked young and older participants to encode the locations of objects in a virtual room shown as a picture on a computer screen. Participants were then shown a second picture of the same room taken from the same (0°) or a different perspective (45° or 135°) and had to judge whether the objects occupied the same or different locations. Overall, older adults had greater difficulty with the task than younger adults although the introduction of a perspective shift between encoding and testing impaired performance in both age groups. Diffusion modelling revealed that older adults adopted a more conservative response strategy, while the analysis of gaze patterns showed an age-related shift in visual-encoding strategies with older adults attending to more information when memorising the positions of objects in space. Overall, results suggest that ageing is associated with declines in spatial processing abilities, with older individuals shifting towards a more conservative decision style and relying more on encoding target object positions using room-based cues compared to younger adults, who focus more on encoding the spatial relationships among object clusters.

Novel Ultrasonographic Thickness and Strength Assessments of the Flexor Digitorum: A Reliability Analysis.

OBJECTIVES: Clinical conditions such as focal dystonia often require the assessment of atrophy and weakness of the finger muscles. However, due to a lack of well-established protocols, the current investigation focused on assessing the reliability of thickness and strength assessments of the flexor digitorum (FD) muscle, including both the superficialis and profundus components. As a secondary assessment, the reliability of the strength measurement of the extensor digitorum muscle was examined as well. METHODS: Different thickness measurements of the FD were taken via ultrasonography and averaged to estimate the mean thickness of the FD. Likewise, individual finger strength measurements taken by a custom-made finger pressure device were averaged to compute the mean strength of the flexor and extensor digitorum muscles. Test-retest reliability of the above measurements performed at two different time points (about 6 months apart) were examined on the right and left hands of 10 participants. RESULTS: Findings indicated excellent test-retest reliability (ICC > 0.92) for the mean thickness assessment of the FD and mean strength of the flexor and extensor digitorum for both dominant and non-dominant hands. The standard error of measurement was ≤4.3% for all three mean assessments, indicating high sensitivity. Likewise, the smallest detectable change was also sufficiently small for the mean thickness and mean strength of the flexor digitorum (≤5.1%) and moderately small (≤12%) for the strength of the extensor digitorum. CONCLUSIONS: Results indicated an excellent relative and absolute reliability, for both hands, for the mean thickness and strength assessments of the flexor digitorum muscle and for the mean strength of the extensor digitorum (measured for both hands). These measurements can be used for future investigations and can contribute to the establishment of more precise methods for assessing the muscles in the forearms which serve the hand.

Orientation-dependent spatial memories for scenes viewed on mobile devices.

We examined whether spatial representations for scenes experienced on the screens of mobile devices are orientation dependent and whether the type of movement (physical vs. simulated) during learning affects the encoding and the retrieval of spatial information. Participants studied a spatial layout depicted on a tablet and then carried out perspective-taking trials in which they localized objects from imagined perspectives. Depending on condition, participants either rotated the tablet along with their body or remained stationary and swiped with their finger on the screen to change their viewpoint within the scene. Results showed that participants were faster and more accurate to point to objects from an imagined perspective that was aligned than misaligned to their initial physical orientation during learning, suggesting that they had formed an orientation-dependent representation. Although no differences were found between movement conditions during pointing, participants were faster to encode spatial information with physical than simulated movement.

Integrating visuospatial information across distinct experiences.

In two experiments, we examined whether the presence of stable visual information and the confluence of the viewpoints would cause participants to integrate in a single memory representation spatial locations they encoded at different points in time. Participants studied from the same or from different viewpoints two layouts of objects within a common visually cluttered room. Then, they carried out a series of pointing trials that involved objects from either the same or different layouts. Results showed that participants were faster for within- than between-layout judgments when they had studied the two layouts from different viewpoints but were equally fast across the two types of judgment after studying the layouts from the same viewpoint (Experiment 1). This finding suggests that they integrated locations into a single representation only when encoding the layouts from the same viewpoint. However, when participants' memory for the layout studied first was refreshed prior to testing (Experiment 2), no difference in response time was found, suggesting that they had integrated all locations in a single representation before the beginning of testing.

Selection of macroreference frames in spatial memory.

Spatial memories are often hierarchically organized with different regions of space represented in unique clusters within the hierarchy. Each cluster is thought to be organized around its own microreference frame selected during learning, whereas relationships between clusters are organized by a macroreference frame. Two experiments were conducted in order to better understand important characteristics of macroreference frames. Participants learned overlapping spatial layouts of objects within a room-sized environment before performing a perspective-taking task from memory. Of critical importance were between-layout judgments thought to reflect the macroreference frame. The results indicate that (1) macroreference frames characterize overlapping spatial layouts, (2) macroreference frames are used even when microreference frames are aligned with one another, and (3) macroreference frame selection depends on an interaction between the global macroaxis (defined by characteristics of the layout of all learned objects), the relational macroaxis (defined by characteristics of the two layouts being related on a perspective-taking trial), and the learning view. These results refine the current understanding of macroreference frames and document their broad role in spatial memory.

Developmental changes in the mental transformation of spatial arrays.

An experiment was conducted to investigate the spatial memory and transformation of spatial relations in a sample of 7-, 9-, and 11-year-olds and to compare their performance with that of adults. Four pictures of animals were presented at different locations on the outline of a circle. Participants were instructed to memorize the array of locations and then, in a direct retrieval task, to reconstruct it from memory on a piece of paper that included only the circle outline. Then, in the transformation task, participants were asked to randomly place one of the animals at a new position around the circle and then to place the remaining three animals so that object-to-object locations were preserved. Results from the direct retrieval task showed that 7-year-olds were less accurate than older children and adults, whereas 9- and 11-year-olds showed comparable performance to each other and to adults in reconstructing the array. Results from the transformation task revealed that adults were more accurate than children and that 11-year-olds were more accurate than 7-year-olds. There was no difference between 9- and 11-year-olds. Overall, these findings suggest that the ability to perform spatial transformations (a) develops gradually during childhood and (b) has a steeper developmental slope than the simple retrieval of memorized spatial information.

Updating spatial relations to remote locations described in narratives.

In four experiments we examined whether sensorimotor encoding influences readers' reasoning about spatial scenes acquired through narratives. Participants read a narrative that described the geometry of a store and then pointed to the memorized locations of described objects from imagined perspectives. In Experiment 1, participants walked during learning towards the direction of every described object and then visualized these objects as being in the immediate environment. In Experiment 2 they rotated their body to the direction of the described objects instead of walking to them, while in Experiment 3 they only turned their heads towards the objects. In Experiment 4, we eliminated the instructions to visualize the objects altogether. Results from the first three experiments revealed a performance benefit for responding from the perspective that participants physically occupied at testing. However, results from Experiment 4 showed that only participants who, in a post-task questionnaire, indicated that they had linked the described environment to their immediate environment exhibited such a benefit. Findings indicate that (1) the physical change in orientation influences reasoning about described environments if the remote environments are linked to participants' sensorimotor framework and, (2) visualization instructions are sufficient to produce such a link.

What's so difficult with adopting imagined perspectives?

Research on spatial cognition suggests that transformation processes and/or spatial conflicts may influence performance on mental perspective-taking tasks. However, conflicting findings have complicated our understanding about the processes involved in perspective-taking, particularly those giving rise to angular disparity effects, whereby performance worsens as the imagined perspective adopted deviates from one's actual perspective. Based on data from experiments involving mental perspective-taking in immediate and remote spatial layouts, we propose here a novel account for the difficulty with perspective-taking. According to this account, the main difficulty lies in maintaining an imagined perspective in working memory, especially in the presence of salient sensorimotor information.

Cross-sensory reference frame transfer in spatial memory: the case of proprioceptive learning.

In three experiments, we investigated whether the information available to visual perception prior to encoding the locations of objects in a path through proprioception would influence the reference direction from which the spatial memory was formed. Participants walked a path whose orientation was misaligned to the walls of the enclosing room and to the square sheet that covered the path prior to learning (Exp. 1) and, in addition, to the intrinsic structure of a layout studied visually prior to walking the path and to the orientation of stripes drawn on the floor (Exps. 2 and 3). Despite the availability of prior visual information, participants constructed spatial memories that were aligned with the canonical axes of the path, as opposed to the reference directions primed by visual experience. The results are discussed in the context of previous studies documenting transfer of reference frames within and across perceptual modalities.

Correction: Visual orientation discrimination skills are tightly linked with specific aspects of human intelligence.

[This corrects the article DOI: 10.1371/journal.pone.0289590.].

Reshaping the peripersonal space in virtual reality.

Peripersonal space (PPS) is defined as the space that lies within reach. Previous research revealed that PPS can be dynamically reshaped with the use of tools extending the arm's reach. Here we investigated whether PPS reshaping depends on the kind of selected tool and/or the motor routine associated with its use. Participants carried out a visuo-tactile detection task in an immersive VR environment that allowed to measure the PPS size before and after a short period of tools use. In Experiment 1, participants had to pull or push objects towards or away from themselves using a shovel. In Experiment 2, they were required to either hammer or shoot an avatar placed in the Extrapersonal space. We found, for the first time in a VR environment, that a period of pull training was effective in enlarging the PPS, a result that replicates and expands previous findings carried out in real life conditions. However, no significant change in PPS size was achieved for training with other tools and motor routines. Our results suggest that the reshaping of PPS is a complex phenomenon in which the kind of interaction between the agent, the targets and the exploited motor routines all play a critical role.

The impact of fine motor activities like playing musical instruments on the thickness and strength of the flexor digitorum muscle.

BACKGROUND: This study aimed to explore the impact of occupational activities involving extensive finger movement on the muscular characteristics of the forearms. In particular, the flexor digitorum (FD) muscular thickness and strength asymmetry between right and left hand were compared between musicians and non-musicians. METHODS: Ultrasonography was employed to measure the thickness of the FD in each hand, while a validated custom-made device was used to assess the strength of the flexor and extensor digitorum (ED). Initially, muscle differences were estimated by computing the asymmetry index between dominant and non-dominant hands. To assess potential occupational disparities, comparisons of the asymmetry index were conducted between 25 right-handed instrumental musicians and 25 right-handed non-musicians. RESULTS: Musicians exhibited lower asymmetry between dominant and non-dominant hands in both FD thickness and ED strength when compared to non-musicians. This effect was particularly pronounced in musicians playing instruments that extensively use the left-hand fingers (e.g., violinists). CONCLUSIONS: Occupational activities, such as playing a musical instrument, can alter forearm muscle mass and strength distribution between dominant and non-dominant hands. This underscores the importance of considering occupational parameters in clinical or experimental interventions and musculoskeletal assessments.

Egocentric updating of remote locations.

The study examined whether people update remote spatial locations in unfamiliar environments during physical movement. Participants learned a layout of objects from one perspective and carried out perspective-taking trials after physically rotating to a new perspective in either the same room as learning or in an adjacent room. Prior to rotation in the adjacent room participants were instructed to visualize the objects as being around them. Responses to perspective-taking trials involved either pointing or verbal labeling. In both testing environments, participants pointed more efficiently from imagined perspectives aligned with either the initial learning perspective or their current facing orientation than from a novel imagined perspective; this indicates that they had updated the encoded spatial relations during the physical rotation and treated remote objects as immediate. Differences in performance among perspectives were less pronounced for verbal labeling in both environments, suggesting that this response mode is more flexibly used from imagined perspectives.

Integrating spatial information across experiences.

The current study examined the potential influence of existing spatial knowledge on the coding of new spatial information. In the Main experiment, participants learned the locations of five objects before completing a perspective-taking task. Subsequently, they studied the same five objects and five additional objects from a new location before completing a second perspective-taking task. Task performance following the first learning phase was best from perspectives aligned with the learning view. However, following the second learning phase, performance was best from the perspective aligned with the second view. A supplementary manipulation increased the salience of the initial view through environmental structure as well as the number of objects present. Results indicated that the initial learning view was preferred throughout the experiment. The role of assimilation and accommodation mechanisms in spatial memory, and the conditions under which they occur, are discussed.

Collaborating in spatial tasks: how partners coordinate their spatial memories and descriptions.

We summarize findings from a study examining whether the availability of the conversational partner's spatial viewpoint influences the speaker's spatial memories, description strategies, their joint efficiency and accuracy on the task, as well as the partner's resulting spatial memories. In 18 pairs, Directors described to a misaligned Matcher arrays that they learned while either knowing their Matcher's viewpoint or not. Memory tests preceding descriptions revealed that Directors represented their Matcher's viewpoint when known in advance. Moreover, Directors adapted the perspective of their descriptions according to each other's cognitive demands, given their misalignment. The number of conversational turns pairs took to coordinate suggested that pairs' strategies were effective at minimizing their collective effort. Nonetheless, in terms of accuracy on the task, pairs reconstructed more distorted arrays the more partner-centered descriptions Directors used. The Directors' descriptions also predicted Matchers' facilitation for their own perspective in memory tests following the description. Together, these findings demonstrate that partners in collaborative spatial tasks adapt their respective memory representations and descriptions contingently with the aim of optimizing coordination.

The effect of visually filled reproductions on the reproduced durations of auditory intervals.

The present study examined how the perception of time is affected by the presence of a visual stimulus during the reproduction phase of an online time reproduction task. Participants were instructed to reproduce the durations of speed-altered speech snippets with either a picture or a blank screen presented during the reproduction phase. Results showed that fast speeches were reproduced as longer than slow ones, while the reproduced durations of short speeches were closer to the actual durations than were the long speeches. In addition, longer reproduced durations were observed in trials with a picture than in trials with a blank screen. These results provide clear evidence that postencoding information can influence the reproduction of previously encoded temporal intervals and are discussed in the context of attention allocation and its possible influence on an internal clock mechanism. Also, the study provides evidence that online testing is reliable for assessing biases in time perception, at least with time reproduction tasks.

Visual orientation discrimination skills are tightly linked with specific aspects of human intelligence.

We investigate the notion that basic visual information is acting as a building block for more complex cognitive processes in humans. Specifically, we measured individual visual orientation discrimination thresholds to report significant correlations against the total standardised intelligence quotient (IQ), verbal-IQ and non-verbal IQ scores evaluated using the Wechsler Abbreviated Scale of Intelligence Second Edition (WASI-II) test battery comprising Verbal Reasoning, Block Design, Similarities and Matrix Reasoning subtests (N = 92). A multiple linear regression analysis showed that participants' performance in our visual discrimination task, could be explained only by individual scores in Verbal Reasoning which quantifies the ability to comprehend and describe words and Matrix Reasoning, which evaluates general visual processing skills including abstract and spatial perception. Our results demonstrate that low-level visual abilities and high-level cognitive processes are more tightly interwoven together than previously thought and this result could pave the way for further research on how cognition can be defined by basic sensory processes.

Music and speech time perception of musically trained individuals: The effects of audio type, duration of musical training, and rhythm perception.

The perception of time is a subjective experience influenced by various factors such as individual psychology, external stimuli, and personal experiences, and it is often assessed with the use of the reproduction task that involves individuals estimating and reproducing the duration of specific time intervals. In the current study, we examined the ability of 97 musically trained participants to reproduce the durations of temporal intervals that were filled with music or speech stimuli. The results revealed a consistent pattern of durations being underestimated, and an association was observed between the duration of musical training and the level of accuracy in reproducing both music and speech tracks. In addition, speech tracks were overall reproduced more accurately, and as longer, than music tracks. Structural models suggested the presence of two, highly correlated, dimensions of time perception for speech and music stimuli that were related to the duration of musical training, but not with self-reported rhythm perception. The possible effects of arousal and pleasantness of stimuli on time perception are discussed within the framework of an internal clock model.

Biases in object location estimation: The role of rotations and translation.

Spatial memory studies often employ static images depicting a scene, an array of objects, or environmental features from one perspective and then following a perspective-shift-prompt memory either of the scene or objects within the scene. The current study investigated a previously reported systematic bias in spatial memory where, following a perspective shift from encoding to recall, participants indicated the location of an object farther to the direction of the shift. In Experiment 1, we aimed to replicate this bias by asking participants to encode the location of an object in a virtual room and then indicate it from memory following a perspective shift induced by camera translation and rotation. In Experiment 2, we decoupled the influence of camera translations and rotations and examined whether adding additional objects to the virtual room would reduce the bias. Overall, our results indicate that camera translations result in greater systematic bias than camera rotations. We propose that the accurate representation of camera translations requires more demanding mental computations than camera rotations, leading to greater uncertainty regarding the location of an object in memory. This uncertainty causes people to rely on an egocentric anchor, thereby giving rise to the systematic bias in the direction of camera translation.